Transistor layout to reduce kink effect

ABSTRACT

The present disclosure, in some embodiments, relates to an integrated chip. The integrated chip includes a substrate having interior surfaces that define a trench within an upper surface of the substrate. One or more dielectric materials are disposed within the trench. A source region disposed within the substrate and a drain region is disposed within of the substrate and separated from the source region along a first direction. A gate structure is over the upper surface of the substrate between the source region and the drain region. The upper surface of the substrate has a first width directly below the gate structure that is larger than a second width of the upper surface of the substrate within the source region or the drain region. The first width and the second width are measured along a second direction that is perpendicular to the first direction.

REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. application Ser. No.15/989,606, filed on May 25, 2018, which claims the benefit of U.S.Provisional Application No. 62/585,636, filed on Nov. 14, 2017. Thecontents of the above-referenced patent applications are herebyincorporated by reference in their entirety.

BACKGROUND

Modern day integrated chips comprise millions or billions ofsemiconductor devices formed on a semiconductor substrate (e.g., asilicon substrate). To improve functionality of integrated chips, thesemiconductor industry has continually reduced the dimension ofsemiconductor devices to provide for integrated chips with small,densely populated devices. By forming integrated chips having small,densely populated devices, the speed of the semiconductor devicesincreases and the power consumption of the semiconductor devicesdecreases.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIGS. 1A-1B illustrate some embodiments of an integrated chip comprisinga transistor device within an active area having a shape configured toimproved device performance.

FIGS. 2A-2B illustrate graphs showing some embodiments of exemplaryperformance parameters of a transistor device having an active area witha disclosed shape.

FIGS. 3A-3D illustrates some additional embodiments of an integratedchip comprising a transistor device within an active area having a shapeconfigured to improved device performance.

FIG. 4 illustrates a top-view showing some alternative embodiments of anintegrated chip comprising a transistor device within an active areahaving a shape configured to improve device performance.

FIGS. 5A-5B illustrate some additional embodiments of an integrated chiphaving different regions with different gate dielectric thicknesses.

FIGS. 6A-11B illustrate some embodiments of cross-sectional views andtop-views corresponding to a method of forming an integrated chipcomprising a transistor device arranged within an active area having ashape configured to improve device performance.

FIG. 12 illustrates a flow diagram of some embodiments of a method offorming an integrated chip comprising a transistor device arrangedwithin an active area having a shape configured to improve deviceperformance.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the provided subjectmatter. Specific examples of components and arrangements are describedbelow to simplify the present disclosure. These are, of course, merelyexamples and are not intended to be limiting. For example, the formationof a first feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

In integrated chips, active devices (e.g., MOSFET devices, embeddedmemory devices, etc.) are generally arranged on a shared semiconductorsubstrate (e.g., a silicon substrate). However, semiconductor materialscan be electrically conductive, such that leakage currents may travelbetween active devices that are located within a semiconductor substratein close proximity to one another. If such leakage currents are notproperly mitigated, cross-talk between adjacent devices can lead tointegrated chip failure.

To prevent leakage currents from traveling between adjacent devices,many modern day integrated chips use shallow trench isolation (STI)structures. Typically, STI structures are formed by forming a pad oxideover a substrate, patterning the pad oxide according to a nitridemasking layer, etching trenches in the substrate according to thenitride masking layer, filling the trenches with one or more dielectricmaterials (such as silicon dioxide or silicon nitride), and removingexcess of the one or more dielectric materials from over the substrate.STI formation processes may furthermore use a wet etching process toremove the nitride masking layer and/or the pad oxide used duringformation of the STI structures.

However, it has been appreciated that during the formation of an STIstructure divots may form within an upper surface of the STI structure(e.g., due to the wet etching process used to remove the nitride maskinglayer and/or pad oxide). Such divots can negatively impact electricalbehavior (e.g., both threshold and sub-threshold voltages) of adjacentdevices, leading to unpredictable performance of the devices. Forexample, during fabrication of a transistor device, a conductive gatematerial can fill divots within an STI structure, causing the conductivegate material to have sharp edges that can enhance an electric fieldgenerated by a gate structure during operation of a transistor device.The enhanced electrical field reduces a threshold voltage of thetransistor device, resulting in a problem called the kink effect (e.g.,defined by a double hump in a drain current vs. gate voltage relation).The kink effect has a number of negative consequences, such as beingdifficult to model (e.g., in SPICE curve fitting and/or parameterextraction).

The present disclosure, in some embodiments, relates to a transistordevice disposed within an active area having a shape configured toreduce a susceptibility of the transistor device to performancedegradation (e.g., the kink effect) caused by divots in an adjacentisolation structure, and an associated method of formation. Thetransistor device comprises a substrate having interior surfacesdefining a trench within an upper surface of the substrate. One or moredielectric materials are arranged within the trench. The one or moredielectric materials define an opening exposing the upper surface of thesubstrate. The opening has a source opening over a source region withinthe substrate, a drain opening over a drain region within the substrate,and a channel opening between the source opening and the drain opening.The source opening and the drain opening have widths that are smallerthan the channel opening. A gate structure extends over the opening at alocation between the source and drain regions. Because the sourceopening and the drain opening have smaller widths than the channelopening, a resulting channel region extending between the source anddrain regions will be separated from edges of the isolation structure bya non-zero distance. Separating the channel region from the edges of theisolation structure by the non-zero distance reduces an effect thatdivots within the isolation structure have on the channel region.

FIGS. 1A-1B illustrate some embodiments of an integrated chip comprisinga transistor device within an active area having a shape configured toimproved device performance.

As shown in cross-section view 100 FIG. 1A, the integrated chipcomprises a substrate 102 having interior surfaces defining a trench 103extending from an upper surface 102 u of the substrate 102 to within thesubstrate 102. An isolation structure 104 (e.g., a shallow trenchisolation (STI) structure) comprising one or more dielectric materialsis disposed within the trench 103. The isolation structure 104 comprisessidewalls defining an opening 106 that exposes the upper surface 102 uof the substrate 102. The opening 106 defines an active area (i.e., anarea of the substrate 102 where a transistor device is located). Theisolation structure 104 further comprises surfaces defining one or moredivots 110 that are recessed below an uppermost surface of the isolationstructure 104. The one or more divots 110 are arranged along an edge ofthe isolation structure 104 that is proximate to the opening 106.

A gate structure 112 is disposed over the substrate 102 and extends pastopposing sidewalls of the isolation structure 104 that define theopening 106. The gate structure 112 comprises a conductive gate material116 separated from the substrate 102 by a gate dielectric 114. Aconductive contact 120 is arranged within a dielectric structure 118(e.g., an inter-level dielectric (ILD) layer) over the substrate 102.The conductive contact 120 vertically extends from the conductive gatematerial 116 to a top of the dielectric structure 118.

As shown in the top-view 122 of FIG. 1B, the isolation structure 104continuously extends around the opening 106 defined by the isolationstructure 104 and the one or more divots 110 are arranged within theisolation structure 104 around the opening 106. The opening 106 has asource opening 106 a that is separated from a drain opening 106 c alonga first direction 128 by a channel opening 106 b. Along a seconddirection 130, the source opening 106 a has a first width W_(S/D_1), thedrain opening 106 c has a second width W_(S/D_2), and the channelopening 106 b has a third width W_(CH) that is larger than the firstwidth W_(S/D_1) and the second width W_(S/D_2). In some embodiments, thefirst width W_(S/D_1) and the second width W_(S/D_2) may besubstantially equal. In some embodiments, a difference between the firstwidth W_(S/D_1) and the third width W_(CH) is greater than or equal toapproximately twice a width of a first one of the one or more divots110.

A source region 124 is disposed within the source opening 106 a and adrain region 126 is disposed within the drain opening 106 c. The sourceregion 124 and the drain region 126 respectively comprise highly dopedregions disposed within an upper surface of the substrate 102. In someembodiments, the source region 124 has a width that is substantiallyequal to the first width W_(S/D_1) and the drain region 126 has a widththat is substantially equal to the second width W_(S/D_2). In someembodiments, the channel opening 106 b extends past opposing sides ofthe source region 124 and the drain region 126 along the seconddirection 130. The gate structure 112 extends over the opening 106 at alocation between the source region 124 and the drain region 126.

During operation, the conductive gate material 116 is configured togenerate an electric field that forms a conductive channel within achannel region 125 extending within the substrate 102 between the sourceregion 124 and the drain region 126. Since the widths of the sourceregion 124 and the drain region 126 are less than the third width W_(CH)of the channel opening 106 b, the channel region 125 has an effectivewidth W_(eff) that is separated from the one or more divots 110 withinthe isolation structure 104 by a non-zero distance ΔW. Separating theeffective width W_(eff) of the channel region 125 from the one or moredivots 110 within the isolation structure 104 by the non-zero distanceΔW reduces an effect of the one or more divots 110 on the electric fieldgenerated by the gate structure 112 along edges of the channel region125. By reducing an effect of the one or more divots 110 on the channelregion 125, a performance of the transistor device is improved (e.g.,the kink effect in the drain current caused by the effect of the one ormore divots 110 on the electric field generated by the gate structure112 is reduced).

FIGS. 2A-2B illustrate graphs, 200 and 204, showing some embodiments ofexemplary performance parameters of the transistor device of FIGS.1A-1B.

Graph 200 of FIG. 2A illustrates an absolute electric field (shown alongthe y-axis) as a function of a position within an active area (shownalong x-axis). Since a channel region (e.g., 125 of FIG. 1B) formed by agate structure (e.g., 112 of FIG. 1B) has an effective width W_(eff)that is less than a width of the channel opening (e.g., 106 b of FIG.1B), the channel region is separated on opposing sides from one or moredivots (e.g., 110 of FIG. 1B) in the isolation structure by a non-zerodistance ΔW.

As shown in graph 200, the absolute electric field within the non-zerodistance ΔW is greater than the absolute electric field within thechannel region. Therefore, by separating the effective width W_(eff) ofthe channel region from the isolation structure by the non-zero distanceΔW, the higher absolute electric field caused by the one or more divotsis separated from the channel region and an effect of the one or moredivots on the absolute electric field 202 generated by the gatestructure on the channel region is reduced.

Graph 204 of FIG. 2B illustrates an absolute threshold voltage (shownalong the y-axis) as a function of a position within the active area(shown along x-axis). As shown in graph 204, reducing an effect of theabsolute electric field on the channel region, reduces a variation ofthe absolute threshold voltage 206 within the channel region. Forexample, if the channel region extended to the isolation structure, theabsolute electric field along edges of the channel region would decreasean absolute threshold voltage of an associated transistor device.However, because the effective width W_(eff) of the channel region isset back from edges of the channel opening, changes in the absolutethreshold voltage are mitigated within the channel region. Mitigatingchanges in the absolute threshold voltage in the channel region alsoreduces the kink effect, and thereby improves performance of thetransistor device.

FIGS. 3A-3D illustrates some additional embodiments of an integratedchip comprising a transistor device within an active area having a shapeconfigured to improved device performance.

As shown in top-view 300 of FIG. 3A, the integrated chip has anisolation structure 104 with sidewalls that define an opening 106 over asubstrate (102 of FIG. 3B) within an active region having a sourceregion 124 and a drain region 126. The opening 106 comprises a sourceopening 106 a and a drain opening 106 c separated along a firstdirection 128 by a channel opening 106 b. The source region 124 has awidth (along a second direction 130) that is substantially equal to awidth of the source opening 106 a and the drain region 126 has a widththat is substantially equal to a width of the drain opening 106 c. Insome embodiments, the opening 106 is substantially symmetric about aline bisecting the source region 124 and the drain region 126. In somealternative embodiments (not shown), the opening 106 may not besymmetric about a line bisecting the source region 124 and the drainregion 126. For example, the channel opening 106 b may extend a greaterdistance past a first side of the source opening 106 a than past anopposing second side of the source opening 106 a.

A gate structure 112 extends over the opening 106 along the seconddirection 130. The gate structure 112 is arranged between the sourceregion 124 and the drain region 126. In some embodiments, sidewallspacers 302 may be arranged along outer sidewalls of the gate structure112. The sidewall spacers 302 comprise one or more dielectric materials.For example, in various embodiments, the sidewall spacers 302 maycomprise an oxide (e.g., silicon oxide), a nitride (e.g., siliconnitride, silicon oxy-nitride, etc.), a carbide (e.g., silicon carbide),or the like. In some embodiments, the gate structure 112 and/or thesidewall spacers 302 may extend along the first direction 128 pastopposing sides of the channel opening 106 b by a first non-zero distance304. In some embodiments, the source region 124 is set back from aboundary between the source opening 106 a and the channel opening 106 bby a second non-zero distance 306, while the drain region 126 is setback from a boundary between the drain opening 106 c and the channelopening 106 b by a third non-zero distance 308.

In some embodiments, the first non-zero distance 304 is greater than thesecond non-zero distance 306 and the third non-zero distance 308. Insome such embodiments, the source region 124 and the drain region 126may extend to below the sidewall spacers 302. In some embodiments, theopening 106 may change from a first width within the source opening 106a to a second width within the channel opening 106 b at a location thatis directly under the sidewall spacers 302. Similarly, the opening 106may transition from a second width within the channel opening 106 b to athird width within the drain opening 106 c at a location that isdirectly under the sidewall spacers 302. In other embodiments (notshown), the opening 106 may transition between widths at a locationbelow the gate structure 112.

FIGS. 3B-3C illustrate cross-sectional views, 310 and 314, of theintegrated chip along cross-sectional lines A-A′ and B-B′. As shown incross-sectional view 310 of FIG. 3B, along cross-sectional line A-A′ theopening 106 has a first width that is substantially equal to aneffective width W_(eff) of a channel region between the source region124 and the drain region 126. As shown in cross-sectional view 314 ofFIG. 3C, along cross-sectional line B-B′ the opening 106 has a secondwidth of W_(eff)+2ΔW, which is greater than the first width by adistance that is equal to twice a non-zero distance ΔW (i.e., 2ΔW).

In some embodiments, a size of the non-zero distance ΔW may be in arange of between approximately 2% and approximately 10% of a size of theeffective width W_(eff). For example, in some embodiments, the non-zerodistance ΔW may have a size of between approximately 10 nm andapproximately 1,000 nm, while the effective width W_(eff) may have asize of between approximately 100 nm and approximately 50,000 nm. Havingthe non-zero distance ΔW greater than approximately 2% of the effectivewidth W_(eff) provides for a large enough distance between the divot andthe channel region so as to decrease an impact of electric field changescaused by the one or more divot 110 on the channel region. Having thenon-zero distance ΔW less than 10% of the effective width W_(eff) keepsa footprint of the transistor device small enough to be cost effective.

In some embodiments, a well region 312 may be disposed within thesubstrate 102 below the opening 106. The well region 312 has a dopingtype that is different than that of the substrate 102. For example, insome embodiments where the transistor device is an NMOS transistor, thesubstrate 102 may have an n-type doping, the well region 312 may have ap-type doping, and the source region 124 and the drain region 126 mayhave the n-type doping. In other embodiments, where the transistordevice is a PMOS transistor, the substrate 102 may have an n-typedoping, the well region 312 may have the n-type doping, and the sourceregion 124 and the drain region 126 may have the p-type doping.

A dielectric structure 118 (e.g., an inter-level dielectric (ILD) layer)is arranged over the substrate 102. In some embodiments, the dielectricstructure 118 may comprise borophosphosilicate glass (BPSG),borosilicate glass (BSG), phosphosilicate glass (PSG), or the like. Aconductive contact 120 vertically extends through the dielectricstructure 118 to the conductive gate material 116. The conductivecontact 120 may comprise tungsten, copper, aluminum copper, or someother conductive material.

FIG. 3D illustrates a cross-sectional view 316 of the integrated chipalong cross-sectional line C-C′ of FIG. 3A. As shown in cross-sectionalview 316, the source region 124 and the drain region 126 arranged withinthe well region 312 on opposing sides of the conductive gate material116.

The channel region 125 has a length L. In some embodiments, the length Lof the channel region 125 is approximately equal to a width of the gatestructure 112. In other embodiments, the length L of the channel region125 is less than a width of the gate structure 112. In some embodiments,source and drain extension regions 318 may protrude outward from thesource region 124 and the drain region 126 to below the sidewall spacers302 and/or the conductive gate material 116. In such embodiments, thechannel region 125 extends between the source and drain extensionregions 318. In some embodiments, a silicide layer 320 may be arrangedon the source region 124 and the drain region 126. In some embodiments,the silicide layer 320 may comprise a nickel silicide, cobalt silicide,titanium silicide, or the like.

Although FIG. 3A illustrates the opening 106 as having rectangularshaped source, drain and channel openings, it will be appreciated thatthe opening may have alternative shapes that form a channel region thatis set back from sides of an isolation structure defining the opening.For example, FIG. 4 illustrates a top-view showing some alternativeembodiments of an integrated chip 400 having a transistor device withisolation structures configured to improve device performance.

The integrated chip 400 comprises an isolation structure 104 defining anopening 402 exposing the substrate 102. The opening 402 defined by theisolation structure 104 has a source region 124 within a source opening402 a and a drain region 126 within a drain opening 402 c. The sourceopening 402 a and the drain opening 402 c are separated by a channelopening 402 b. The channel opening 402 b has a width that graduallychanges from the first width W_(S/D) to a second width W_(CH). In someembodiments, the isolation structure 104 has angled sidewalls thatdefine the channel opening 402 b and that gradually increase a width ofthe channel opening 402 b in a linear manner. Gradually increasing awidth of the channel opening 402 b in a linear manner allows for adistance between a channel region and the one or more divots 110 to bekept relatively large in spite of alignment errors. For example, if thegate structure 112 is misaligned along a first direction 128, the sizeof the source region 124 or the drain region 126 along a seconddirection 128 is limited by the gradual increase in the width of thechannel opening 402 b, thereby keeping the channel region from away fromthe divots along edges of the channel opening 402 b. In someembodiments, the angled sidewalls are set back from an outer edge of thegate structure 112 by a non-zero distance 404. In other embodiments (notshown), the isolation structure 104 may have curved sidewalls (viewedfrom a top-view) that define the channel opening 402 b. For example, theisolation structure 104 may have sidewalls that have a slope (viewedfrom a top-view) with an absolute value that increases as a distancefrom the source region 124 or the drain region 126 decreases.

FIGS. 5A-5B illustrate some additional embodiments of an integrated chiphaving different regions with different gate dielectric thicknesses. Ithas been appreciated that the formation of multiple gate dielectriclayers within different regions of an integrated chip may increase asize of divots within isolation structures due to the additional etchprocesses, thereby aggravating the kink effect within associatedtransistor devices. For example, in some processes used to form multiplegate dielectric layers, a gate oxide may be thermally grown on asubstrate (but not on surrounding isolation structures). The gate oxidemay be subsequently removed from the substrate in some device regionsthat use a different gate dielectric layer. Removal of the gate oxide isdone by an etch that also acts on the surrounding isolation structures.Due to over etching, the removal of the gate oxide may increase a sizeof divots within the isolation structures.

The integrated chip comprises a substrate 102 having a first logicregion 502, an embedded memory region 512, and a second logic region522. Isolation structures 104 are arranged within the substrate 102within the first logic region 502, the embedded memory region 512, andthe second logic region 522. In some embodiments, the first logic region502 comprises a high voltage transistor device that is configured toprovide a higher breakdown voltage than a dual gate transistor devicearranged within the second logic region 522.

As shown in cross-sectional view 500 of FIG. 5A, the isolation structure104 within the first logic region 502 has sidewalls defining an opening106 exposing a first upper surface of the substrate 102. A high voltagegate electrode 508 is arranged over the opening 106 and is verticallyseparated from a substrate 102 by way of a high voltage gate dielectriclayer 504 and a dual-gate dielectric layer 506 having a first gatedielectric layer 506 a and a second gate dielectric layer 506 b. In someembodiments, the high voltage gate electrode 508 is vertically separatedfrom a high voltage well 510 disposed within the substrate 102. In someembodiments, the substrate 102 may have a first doping type and the highvoltage well 510 may have a second doping type. As shown in top-view 530of FIG. 5B, the opening 106 in the first logic region 502 is largerbelow the high voltage gate electrode 508 than within a source region124 or a drain region 126.

As shown in cross-sectional view 500 of FIG. 5A, the isolation structure104 within the embedded memory region 512 has sidewalls defining anopening 514 exposing a second upper surface of the substrate 102. Insome embodiments, a control gate electrode 518 is arranged over theopening 514 and is separated from the substrate 102 by the dual-gatedielectric layer 506 and a charge trapping dielectric structure 516. Insome embodiments, the charge trapping dielectric structure 516 maycomprise an ONO structure having a nitride layer disposed between afirst oxide layer and a second oxide layer. In some embodiments, thecontrol gate electrode 518 is vertically separated from a control well520 disposed within the substrate 102. As shown in top-view 530 of FIG.5B, the embedded memory region 512 may also comprise a select gateelectrode 532. In some embodiments, the control gate electrode 518 andthe select gate electrode 532 share a common source/drain region 534.Although the embedded memory region 512 of FIGS. 5A-5B is illustrated ascomprising a SONOS flash memory device, it will be appreciated that inother embodiments, the embedded memory region 512 may comprise differenttypes of memory devices. For example, in other embodiments, the embeddedmemory region 512 may comprise a different type of flash memory device,such as a floating gate flash memory device, a split gate flash memorydevice, etc.), or the like.

As shown in cross-sectional view 500 of FIG. 5A, the isolation structure104 within the second logic region 522 has sidewalls defining an opening524 exposing a third upper surface of the substrate 102. A logic gateelectrode 526 is vertically separated from the substrate 102 by the dualgate dielectric layer 506. In some embodiments, the logic gate electrode526 is vertically separated from a logic well 528 disposed within thesubstrate 102. As shown in top-view 530 of FIG. 5B, the logic gateelectrode 526 extends between a source region 536 and a drain region 538arranged within the opening 524 within the second logic region 522. Insome embodiments, the opening 524 within the second logic region 522 maybe substantially rectangular. In other embodiments (not shown), theopening 524 within the second logic region 522 may have a greater widthbelow the logic gate electrode 526 than around the source region 536and/or the drain region 538.

FIGS. 6A-11B illustrate some embodiments of cross-sectional views andtop-views corresponding to a method of forming an integrated chipcomprising a transistor device arranged within an active area having ashape configured to improve device performance. By using the shape ofthe active area to improve device performance, the method is able to beperformed at a low cost since it does not require additional masksand/or processing steps. Furthermore, it is compatible with existingprocess flows. Although FIGS. 6A-11B are described with reference to amethod, it will be appreciated that the structures shown in FIGS. 6A-11Bare not limited to the method but rather may stand alone separate of themethod.

As shown in top-view 600 of FIG. 6A and cross-sectional view 602 of FIG.6B, an isolation structure 104 is formed within a trench 103 within asubstrate 102. The isolation structure 104 has sidewalls that define anopening 106 that exposes an upper surface 102 u of the substrate 102. Asshown in top-view 600 of FIG. 6A, the opening 106 has a source opening106 a, a drain opening 106 c, and a channel opening 106 b. The channelopening 106 b is arranged between the source opening 106 a and the drainopening 106 c along a first direction 128. The source opening 106 a andthe drain opening 106 c have smaller widths than the channel opening 106b along a second direction 130 that is perpendicular to the firstdirection 128. As shown in cross-sectional view 602 of FIG. 6B, thetrench 103 defined by interior surfaces of the substrate 102. Duringformation of the isolation structures 104, one or more divots 110 may beformed within a top of the isolation structure 104. The one or moredivots 110 may be arranged along an edge of the isolation structure 104that is proximate to the opening 106.

In some embodiments, the isolation structure 104 may be formed byselectively etching the substrate 102 to form the trench 103. One ormore dielectric materials are subsequently formed within the trench 103.In various embodiments, the substrate 102 may be selectively etched by awet etchant (e.g., hydrofluoric acid, potassium hydroxide, or the like)or a dry etchant (e.g., having an etching chemistry comprising fluorine,chlorine, or the like). In various embodiments, the substrate 102 may beany type of semiconductor body (e.g., silicon, SiGe, SOI, etc.), as wellas any other type of semiconductor, epitaxial, dielectric, or metallayers, associated therewith. In various embodiments, the one or moredielectric materials may comprise an oxide, a nitride, a carbide, or thelike.

In some additional embodiments, the isolation structure 104 may beformed by using a thermal process to form a pad oxide over the substrate102, followed by the formation of a nitride film over the pad oxide. Thenitride film is subsequently patterned (e.g., using a photosensitivematerial, such as photoresist), and the pad oxide and substrate 102 arepatterned according to the nitride film to form the trench 103 withinthe substrate 102. The trench 103 is then filled with one or moredielectric materials, followed by a planarization process (e.g., achemical mechanical planarization process) to expose a top of thenitride film and an etch to remove the nitride film.

As shown in top-view 700 of FIG. 7A and cross-sectional view 702 of FIG.7B, a gate dielectric 114 is formed over the substrate 102 and withinthe opening 106. In some embodiments, the gate dielectric 114 maycomprise an oxide (e.g., silicon oxide), a nitride (e.g., siliconoxy-nitride), or the like. In some embodiments, the gate dielectric 114may be formed by way of a vapor deposition technique (e.g., PVD, CVD,PE-CVD, ALD, etc.). In other embodiments, the gate dielectric 114 may beformed by way of a thermal growth process. In some embodiments, animplantation process may be performed prior to the formation of the gatedielectric 114 to form a well region (not shown) in the substrate 102.In some such embodiments, a sacrificial dielectric layer (not shown) maybe formed over the substrate 102 prior to the implantation process toregulate a depth of the well region. The sacrificial dielectric layer issubsequently removed prior to formation of the gate dielectric.

In some embodiments, the gate dielectric 114 may be formed as part of amultiple gate dielectric process, in which different gate dielectriclayers are formed within different regions of the substrate 102. Forexample, in some embodiments, the multiple gate dielectric process mayform a high voltage gate dielectric layer (e.g., by a thermal process)over a high voltage well within the substrate 102. The high voltage gatedielectric layer may be subsequently removed from one or more regions ofa chip (e.g., within an embedded memory region), and a dual-gatedielectric layer may be formed over a logic well within the substrate102 (e.g., by one or more deposition processes). It has been appreciatedthat the formation of multiple gate dielectric layers may increase asize of the one or more divots 110 within the isolation structures 104due to the additional etch processes that are performed to remove thegate dielectric layers from different regions of the substrate, therebyaggravating the kink effect within associated transistor devices.

As shown in top-view 800 of FIG. 8A and cross-sectional view 802 of FIG.8B, a conductive gate material 116 is formed over the gate dielectric114 and within the divots in the isolation structure 104. The conductivegate material 116 may be formed by way of a deposition process (e.g.,CVD, PE-CVD, PVD, or ALD). In some embodiments, the conductive gatematerial 116 may comprise doped polysilicon. In some embodiments (notshown), the conductive gate material 116 may comprise a sacrificial gatematerial that is subsequently replaced with a metal gate material, suchas aluminum, cobalt, ruthenium, or the like.

As shown in top-view 900 of FIG. 9A and cross-sectional views 902 and904 of FIGS. 9B-9C (respectively along cross-sectional lines A-A′ andB-B′), the gate dielectric 114 and the conductive gate material 116 arepatterned to define a gate structure 112 extending over the opening 106and over the isolation structure 104. The gate structure 112 may fillthe one or more divots 110 within the upper surface of the isolationstructure 104.

The gate dielectric 114 and the conductive gate material 116 may beselectively patterned according to a masking layer (not shown) formedover the conductive gate material 116. In some embodiments, the maskinglayer may comprise a photosensitive material (e.g., photoresist) formedby a spin coating process. In such embodiments, the layer ofphotosensitive material is selectively exposed to electromagneticradiation according to a photomask. The electromagnetic radiationmodifies a solubility of exposed regions within the photosensitivematerial to define soluble regions. The photosensitive material issubsequently developed to define openings within the photosensitivematerial by removing the soluble regions. In other embodiments, themasking layer may comprise a hard mask layer (e.g., a silicon nitridelayer, a silicon carbide layer, or the like).

In some embodiments, one or more sidewall spacers 302 are formed onopposing sides of the gate structure 112. In some embodiments, the oneor more sidewall spacers 302 may be formed by depositing a spacermaterial (e.g., a nitride or an oxide) onto horizontal and verticalsurfaces of the gate structure 112, and subsequently etching the spacermaterial to remove the spacer material from the horizontal surfaces toform the one or more sidewall spacers 302. In some embodiments, the gatestructure 112 and/or the sidewall spacers 302 may extend past opposingsides of the channel opening 106 b by a first non-zero distance 304.

As shown in top-view 1000 of FIG. 10A and cross-sectional views 1002 ofFIG. 10B, a source region 124 and a drain region 126 are formed withinthe substrate 102 on opposing sides of the gate structure 112 along afirst direction 128. The source region 124 comprises a first doping type(e.g., an n-type doping) that is different than a second doping type(e.g., a p-type doping) surrounding the source region 124. For example,the source region 124 may comprise a first doping type within asubstrate 102 or well region (not shown) having a second doping type. Insome embodiments, the source region 124 is set back from a boundarybetween the source opening 106 a and the channel opening 106 b by asecond non-zero distance 306 and the drain region 126 is set back from aboundary between the drain opening 106 c and the channel opening 106 bby a third non-zero distance 308. By setting the source region 124 andthe drain region 126 back from the channel opening 106 b (along thefirst direction 128), the source region 124 and the drain region 126have widths that are less than a width of the channel opening 106 b. Thesmaller widths of the source region 124 and the drain region 126 causethe source region 124 and the drain region 126 to also be set back fromsidewalls of the isolation structure 104 defining the channel opening106 b by a non-zero distance ΔW along a second direction 130 that issubstantially perpendicular to the first direction 128. Setting thesource region 124 and the drain region 126 back from sidewalls of theisolation structure 104 separates a channel region (between the sourceregion 124 and the drain region 126) from the one or more divots 110within the isolation structure 104, and thereby decreases an effect theone or more divots 110 have on an electric field generated by the gatestructure 112 within the channel region. In some embodiments, the sourceregion 124 and the drain region 126 may be formed by an implantationprocess. The implantation process may be performed by selectivelyimplanting a dopant species 1004 into the substrate 102 according to amask comprising the conductive gate material 116 and the sidewallspacers 302. In various embodiments, the dopant species 1004 maycomprise a p-type dopant (e.g., boron, gallium, etc.) or an n-typedopant (e.g., phosphorus, arsenic, etc.). In some embodiments, afterimplanting the dopant species 1004 into the substrate 102, a drive-inanneal may be performed to diffuse the dopant species 1004 within thesubstrate 102. In some embodiments, one or more addition implantationprocesses may be performed to form source and drain extension regions318 within the substrate. In such embodiments, the one or more additionimplantation processes may comprise angled implantation processes sothat the source and drain extension regions 318 extend below the gatestructure 112.

As shown in top-view 1100 of FIG. 11A and cross-sectional view 1102 ofFIG. 11B, a dielectric structure 118 (e.g., an inter-level dielectric(ILD) layer) is formed over the substrate 102. The dielectric structure118 may comprise an oxide, PSG, a low κ dielectric, or some otherdielectric, and may be formed by vapor deposition process (e.g., CVD,PE-CVD, PVD, or ALD). A conductive contact 120 is formed within thedielectric structure 118. The conductive contact 120 may extend from atop surface of the dielectric structure 118 to the conductive gatematerial 116, the source region 124, or the drain region 126. In someembodiments, the dielectric structure 118 may be formed by selectivelyetching the dielectric structure 118 to form an opening. The opening issubsequently filled with a conductive material. In some embodiments, aplanarization process (e.g., a chemical mechanical polishing process)may be performed after filling the opening with the conductive materialto co-planarize upper surfaces of the dielectric structure 118 and theconductive contact 120. In various embodiments, the conductive materialmay comprise tungsten, copper, aluminum copper, or some other conductivematerial.

A contact etch stop layer 1104 may be formed over the substrate 102prior to the formation of the dielectric structure 118. In variousembodiments, the contact etch stop layer 1104 may comprise an oxide, anitride, a carbide, or the like. In some embodiments, wherein theconductive gate material 116 comprises polysilicon, the contact etchstop layer 1104 may extend over an upper surface of the conductive gatematerial 116. In other embodiments (not shown), wherein the conductivegate material 116 comprises a metal gate (e.g., an aluminum gate), thecontact etch stop layer 1104 may not extend over the upper surface ofthe conductive gate material 116. For example, during the formation of aconductive gate material 116 comprising a metal gate, a sacrificial gatestructure may formed over the substrate 102 followed by the formation ofa contact etch stop layer and a first ILD layer. A first CMP process issubsequently performed to expose a top of the sacrificial gate structureby removing the contact etch stop layer and the ILD layer from over thesacrificial gate structure. The sacrificial gate structure is thenremoved and replaced with a metal gate followed by a second CMP processand subsequent formation of a contact within a second ILD layer over thefirst ILD layer.

FIG. 12 illustrates a flow diagram of some embodiments of a method 1200of forming an integrated chip comprising a transistor device arrangedwithin an active area having a shape configured to improve deviceperformance.

While the disclosed method 1200 is illustrated and described herein as aseries of acts or events, it will be appreciated that the illustratedordering of such acts or events are not to be interpreted in a limitingsense. For example, some acts may occur in different orders and/orconcurrently with other acts or events apart from those illustratedand/or described herein. In addition, not all illustrated acts may berequired to implement one or more aspects or embodiments of thedescription herein. Further, one or more of the acts depicted herein maybe carried out in one or more separate acts and/or phases.

At 1202, an isolation structure is formed within a substrate. Theisolation structure comprises sidewalls defining an active area having asource opening with a first width, a drain opening with a second width,and a channel opening with a third width larger than the first andsecond widths. The isolation structure also comprises surfaces definingone or more divots recessed below an uppermost surface of the isolationstructure. FIGS. 6A-6B illustrate some embodiments corresponding to act1202.

At 1204, a gate structure is formed to extend over the channel opening.FIGS. 7A-9C illustrate some embodiments corresponding to act 1204.

At 1206, source and drain regions are formed within the source openingand the drain opening. FIGS. 10A-10B illustrate some embodimentscorresponding to act 1206.

At 1208, a dielectric structure is formed over the substrate. FIGS.11A-11B illustrate some embodiments corresponding to act 1208.

At 1210, a conductive contact is formed within the dielectric structure.FIGS. 11A-11B illustrate some embodiments corresponding to act 1210.

Accordingly, in some embodiments, the present disclosure relates to atransistor device within an active area having a shape configured toreduce a susceptibility of a transistor device to the kink effect causedby divots in an isolation structure, and an associated method offormation.

In some embodiments, the present disclosure relates to an integratedchip. The integrated chip includes a substrate having interior surfacesthat define a trench within an upper surface of the substrate; anisolation structure including one or more dielectric materials withinthe trench and having sidewalls that define an opening exposing theupper surface of the substrate, the opening has a source opening with afirst width, a drain opening with a second width, and a channel openingwith a third width larger than the first width and the second width; asource region disposed within the substrate within the source opening; adrain region disposed within the substrate within the drain opening; anda gate structure extending over the opening at a location between thesource region and the drain region. In some embodiments, the isolationstructure has surfaces defining a one or more divots recessed below anuppermost surface of the isolation structure along an edge of theisolation structure that is proximate to the opening. In someembodiments, the source region is separated from the drain region alonga first direction; a first one of the one or more divots comprises afirst segment extending within the isolation structure along the firstdirection and a second segment extending within the isolation structurealong a second direction that is perpendicular to the first direction;and a line extending along a boundary between the source opening and thedrain opening intersects the second segment. In some embodiments, adifference between the first width and the third width is greater thanor equal to approximately twice a width of a first one of the one ormore divots. In some embodiments, the gate structure is configured togenerate a channel region that extends within the substrate between thesource region and the drain region; and opposing edges of the channelregion are separated from the isolation structure by a non-zerodistance. In some embodiments, the channel opening extends past thesource opening and the drain opening in opposite directions. In someembodiments, the integrated chip further includes sidewall spacersarranged along outer sidewalls of the gate structure, the openingtransitions between the first width and the third width at a positionthat is directly below the sidewall spacers. In some embodiments, thegate structure straddles the channel opening along a first direction andalong a second direction that is perpendicular to the first direction.In some embodiments, the source region is separated from the channelopening by a first non-zero distance and the drain region is separatedfrom the channel opening by a second non-zero distance. In someembodiments, the opening is substantially symmetric about a linebisecting the source region and the drain region. In some embodiments,the first width is substantially equal to the second width. In someembodiments, the opening transitions between the first width and thethird width at a position that is directly below the gate structure.

In other embodiments, the present disclosure relates to an integratedchip. The integrated chip includes an isolation structure arrangedwithin a substrate and having surfaces defining one or more divotsrecessed below an uppermost surface of the isolation structure, theisolation structure defines an opening exposing the substrate; a sourceregion disposed within the opening; a drain region disposed within theopening and separated from the source region along a first direction,the opening extends past opposing sides of the source region along asecond direction perpendicular to the first direction; and a gatestructure extending over the opening along the second direction. In someembodiments, a first one of the one or more divots includes a firstsegment extending within the isolation structure along the firstdirection and a second segment extending within the isolation structurealong the second direction; and a line extending along a boundarybetween the source opening and the drain opening intersects the secondsegment. In some embodiments, the gate structure is configured togenerate a channel region that extends within the substrate between thesource region and the drain region; and opposing edges of the channelregion are separated from the isolation structure by a non-zerodistance. In some embodiments, the opening includes a source openingover the source region and having a first width defined by a first pairof sidewall of the isolation structure; a drain opening over the drainregion and having a second width defined by a second pair of sidewallsof the isolation structure; and a channel opening between the sourceopening and the drain opening and having a third width defined by athird pair of sidewalls of the isolation structure larger, the thirdwidth is larger than the first width and the second width. In someembodiments, the integrated chip further includes sidewall spacersarranged along outer sidewalls of the gate structure, the openingtransitions between the first width and the third width at a positionthat is directly below the sidewall spacers.

In yet other embodiments, the present disclosure relates to a method offorming an integrated chip. The method includes forming an isolationstructure within a substrate, the isolation structure defines a sourceopening, a drain opening, and a channel opening arranged between thesource opening and the drain opening along a first direction andextending past the source opening and the drain opening along a seconddirection perpendicular to the first direction; forming a gate structureover the channel opening; and performing an implantation process to forma source region within the source opening and a drain region within thedrain opening, source region and the drain region set back fromsidewalls of the isolation structure defining the channel opening by anon-zero distance along the second direction. In some embodiments, theisolation structure has surfaces defining one or more divots recessedbelow an uppermost surface of the isolation structure along an edge ofthe isolation structure that is proximate to the opening. In someembodiments, the gate structure is configured to generate a channelregion that extends within the substrate between the source region andthe drain region; and opposing edges of the channel region are separatedfrom the isolation structure by a non-zero distance.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. An integrated chip, comprising: a substratehaving interior surfaces that define a trench within an upper surface ofthe substrate; one or more dielectric materials disposed within thetrench; a source region disposed within the substrate; a drain regiondisposed within the substrate and separated from the source region alonga first direction; and a gate structure over the upper surface of thesubstrate between the source region and the drain region, wherein theupper surface of the substrate has a first width directly below the gatestructure that is larger than a second width of the upper surface of thesubstrate within the source region or the drain region, the first widthand the second width measured along a second direction that isperpendicular to the first direction.
 2. The integrated chip of claim 1,wherein the first width is larger than widths of the upper surface ofthe substrate within both the source region and the drain region.
 3. Theintegrated chip of claim 1, wherein the one or more dielectric materialshave sidewalls that meet at twelve or more corners surrounding the uppersurface of the substrate as viewed from a top-view of the substrate. 4.The integrated chip of claim 1, wherein the gate structure is disposeddirectly over a point where edges of the upper surface of the substrateintersect.
 5. The integrated chip of claim 1, wherein the gate structureis configured to generate a conductive channel extending between thesource region and the drain region, the conductive channel separatedfrom the one or more dielectric materials by a non-zero distancemeasured along the second direction.
 6. The integrated chip of claim 5,wherein the gate structure is configured to generate an electric fieldhaving a first value within the conductive channel and a second valuelaterally between the conductive channel and the one or more dielectricmaterials, wherein the second value is larger than the first value. 7.The integrated chip of claim 1, wherein the gate structure is configuredto generate a conductive channel extending between the source region andthe drain region; and wherein the gate structure has a protrusionextending outward from a lower surface of the gate structure facing thesubstrate, the protrusion laterally separated from the conductivechannel by the substrate.
 8. The integrated chip of claim 1, wherein thesecond width extends between outer edges of the upper surface of thesubstrate directly below the gate structure.
 9. The integrated chip ofclaim 1, wherein the one or more dielectric materials comprise sidewallsdefining one or more divots recessed below an uppermost surface of theone or more dielectric materials; and wherein the sidewalls continuouslyextend in a pattern having a cross like shape.
 10. An integrated chip,comprising: an isolation structure disposed within a substrate andsurrounding an upper surface of the substrate, wherein the upper surfaceof the substrate has outer edges defining a cross shape as viewed from atop-view of the substrate; a gate structure disposed over the uppersurface of the substrate; a source region disposed within the substratealong a first side of the gate structure; and a drain region disposedwithin the substrate along a second side of the gate structure opposingthe first side.
 11. The integrated chip of claim 10, wherein the gatestructure continuously extends from directly over the upper surface ofthe substrate to directly over the isolation structure.
 12. Theintegrated chip of claim 10, wherein the gate structure continuouslyextends from over the upper surface of the substrate to below the uppersurface of the substrate.
 13. The integrated chip of claim 10, wherein awidth of the upper surface of the substrate varies between multipledifferent widths between the source region and the drain region.
 14. Theintegrated chip of claim 10, wherein the isolation structure comprisesinterior surfaces defining one or more divots recessed below anuppermost surface of the isolation structure; and wherein the uppersurface of the substrate separates the one or more divots from a channelregion that is between the source region and the drain region.
 15. Theintegrated chip of claim 14, further comprising: one or more conductivecontacts disposed on the gate structure at one or more positionslaterally separated from the upper surface of the substrate by the oneor more divots.
 16. An integrated chip, comprising: a source regiondisposed within a substrate; a drain region disposed within thesubstrate and separated from the source region along a first direction;an isolation structure disposed within the substrate and surrounding thesource region and the drain region; a gate structure disposed over thesubstrate between the source region and the drain region; and wherein animaginary line, which extends along an edge of the source region or thedrain region facing a second direction that is perpendicular to thefirst direction, is separated from the isolation structure by a non-zerodistance along the second direction.
 17. The integrated chip of claim16, wherein the gate structure is configured to generate an electricfield that forms a conductive channel that extends within the substratebetween the source region and the drain region; and wherein opposingedges of the conductive channel are separated from the isolationstructure by the substrate.
 18. The integrated chip of claim 16, whereinthe isolation structure comprises interior surfaces defining one or moredivots recessed below an uppermost surface of the isolation structure;and wherein the one or more divots are separated from a conductivechannel by an upper surface of the substrate.
 19. The integrated chip ofclaim 16, wherein the isolation structure comprises interior sidewallsdisposed directly over the isolation structure and extending in thefirst direction and in the second direction.
 20. The integrated chip ofclaim 16, wherein the gate structure is directly over both a firstsidewall of the isolation structure extending in the first direction anda second sidewall of the isolation structure extending in the seconddirection.